Drag and Drop

I have an Image control on which I am drawing. No problem.

Now I want to take a Button at the top of the Window and drag this onto the Image. How do I make the button "draggable" as everything I have tried does not work.

I tried this in the Init of the Window but no joy:

BTN_Show..DndSource = dndProgram
IMG_Drawing..DndTarget = dndProgram

DnDEvent(OnDrop, IMG_Drawing, dndDrop)

where "OnDrop" changes the X/Y coordinates of Btn_Show

Thx